2-arylidene-1,3-dithioles and preparation thereof from acethylenes,carbon disulfide,and aromatic aldehydes in the presence of aliphatic phosphines

ABSTRACT

DISCLOSED HEREIN IS A NEW PROCESS FOR MAKING 2-ARYLIDENE-1,3-DITHIOLES, NOVEL PRODUCTS MADE THEREBY AND A UTILITY FOR THE PRODUCTS, I.E., THE INHIBITION OF VINYL POLYMERIZATION. THE PROCESS COMPRISES REACTING AN AROMATIC ALDEHYDE OR DIALDEHYDE WITH CARBON DISULFIDE AND AN ACETYULENIC COMPOUND IN THE PRESENCE OF A TRIHYDROCARBYPHOSPHINE.

United States Patent [Ce 3,781,281

Patented Dec. 25, 1973 X and Y are hydrogen, lower alkoxycarbonyl,phenyl, 3,781,281 carboxyl, cyano, or lower perfiuoroalkyl;

Z-ARYLIDENE 1,3-DlTHI0LES AND PREPARA- the Rs, which may be the same ordifferent are lower TION THEREOF FROM ACETYLENES CAR- BON DISULFIDE, ANDAROMATIC ALDE alkyl, cycloalkyl of 5 or 6 carbons or phenyl(lower HYDESIN THE PRESENCE OF ALIPHATIC 5 alkyl) PHOSPHINES n is 0 o Harris DaleHartzler, Wilmington, DeL, assignor to E. I. r du Pont de Nemours andCompany, Wilmington, Del. 1s 0 or No Drawing. Continuation-impart ofabandoned applical-"1) 1S and tion Ser. No. 55,596, July 16, 1970. Thisapplication 10 m 18 0 1 NOV. 8, 1972, Ser. No. 304,596

Int. Cl- C07d 71/00 In these definitions, lower indicates a group havingUS. Cl. 260-240 F Claims from 1 through 7 carbons.

The novel products contemplated herein are all those 2- ABSTRACT OF THEDISCLOSURE 15 arylidene-1,3-dithioles having the structure representedabove with the provisos that: when Y=H, (m+n )=1, Disclosed herein is anew process for making Z-aryliand m=O, then X phenyl; and when X=H, (n+n)=1,

dene-1,3-dithioles, novel products made thereby and a and m=O, then Y-,-phenyl. utility for the products, i.e., the inhibition of vinylpolymerization. The process comprises reacting an aromatic 20DESCRIPTION OF THE PREFERRED aldehyde or dialdehyde with carbondisulfide and an EMBODIMENTS acetylenic compound in the presence of atrihydrocarbylphosphine, The novel process of this invention comprisescontacting land lc'leagiindg an aromatic aldehyde or dialdehyde withcaron is fi e and an acetylenic compound in the presence RELATEDAPPLICATION of a trihydrocarbylphosphine. The carbon disulfide and Thisapplication is a continuation-in-part of my 00- phosphines apparentlyreact to form a loose complex, pending application Ser. No. 55,596,filed July 16, 1970, R P-CS It is this loose complex with which thealdehyde now abandoned. and acetylenic compound react to form the novelcom- BACKGROUND OF THE INVENTION pounds herein. The phosphine acceptsthe oxygen originally present in the aldehyde and is oxidized to thecorre- Field Of lihe invention sponding oxide, R PO. Although noparticular order of This invention encompasses a new process for makingreactant addition is necessary, it is preferred that the loose2-arylidene-1,3dithioles (otherwise, 5-aryl-1,4 dithiaful- P bePreformed and that the aldehyde and acetylvenes) and the novel productsmade thereby. mm compound be added thereto- Mole ratios of reactants arenot critical. For good prod- (2) Descnpuon of the Prior art u'ct yields,however, a mole ratio of about 1/1, or greater,

Kirmse and Homer, Ann., 614, 4 (1958), have em- CS /phosphine, should beemployed. For best results, it is ployed radiation to prepare certain2-arylidene-1,3-dithi- Preferred to employ a mole ratio of between ut 1-oles, according to the following representation: 40 and z p p y,stoichiometfic amounts. Q of carbon disulfide, aldehyde and acetylenewill be used, radiation but excesses of any one or two of thesereactants can be N 0:0 used if desired s Q S- -Q.' Because of thereactivity of the phosphmes toward As can readily be seen, both Qsubstituents in the product y 1t is desirable, although t absolutelynecessary. must be identical, as must both Q substituents. In contoOperate in an inert atmosphere Such as nitrogen until formance with thearylidenedithiole structure, furtherthe PhOSPhiHe Carbon disulfide havebeen mixedmore, either the Q or the Q substituent must be hydrogen.There is no need for an inert atmosphere thereafter.

Such products are not contemplated herein as such, al- Inert solvent ordiluent Call used if desired, P though they can be made by the disclosednovel process: ticularly when one or more of the reactants arerelatively see Example 23. higggl-meltiiag.h Excess clalrbonldisulfidedcatrlilbe used asda me ium. 1 t er opera e so vents an iuents incu eSUMMARY OF THE INVENTION others, such as ethyl ether, butyl ether,tetrahydrofuran,

The products and process of this invention can be better and1,2-dimethoxyethane; nitriles, such as acetonitrile and understood withreference to the following equation and propionitrile; esters, such asethyl acetate and methyl structural representations: propionate;hydrocarbons, such as benzene, toluene, pen- (CHO) A CH CH) (CHO) )(CS))(X G 0 Y) (H-110K313 n l' n l1 l1 l1 l1 E g m l 1 2 1trihydroearbylphosphiue aromatic aldehyde, dialdehyde carbon disulfideacetylenic compound 2-arylidene-1,3-dithioles (or,5-aryl-1,4-dithiafulvenes) wherein tane, and heptane; and halogenatedhydrocarbons, particuis a monovalent divalent benzene radical unsubstilarly chlorinated hydrocarbons, such as chlorobenzene and tuted orsubstituted with halogen, lower alkyl, lower liz'dlchlol'oethanealkoxy,or nitro, or a monovalent or divalent pyridine The process can beoperated at temperatures between radical; about 50 C. and 200 C.Preferably the temperature 3 will be between about -20 C. and 150 C. Thetemperature will depend in part on the nature of the acetylenicreactant. For example, phenyl-substituted acetylenes usually requirehigher temperatures than alkoxycarbonylsubstituted acetylenes.

The process is conveniently operated in an open system at atmosphericpressure or under the autogenous pressure of a closed system. Higher orlower pressures can be used, but usually not advantage results.

The time required will vary greatly, depending on the temperature andthe nature of the reactants, especially the acetylenic reactant. In somecases, the process will be essentially complete as soon as the reactantsare mixed at room temperature. Even so, the reaction mixture is usuallymaintained for about 15 to 30 minutes to insure a complete reaction.Other systems may require several days to give a good yield of product.The progress of the reaction can be followed by any of a number of knownmethods, such as by infrared analysis of aliquot samples.

Contemplated aldehydes are those in which one or more -CHO groups arebonded to one or more nuclear carbons of an aromatic compound, eitherdirectly, or through a vinylene group. It is preferred that the CH groupor groups be bonded directly to Ar. Cinnamaldehyde, C H CH=CHCHO,however, is a reactant wherein a --CHO group is bonded to Ar through a.vinylene group.

Aldehydes included within the scope of this invention are:

0-, m-, and p-bromobenzaldehyde 3-bromo-4butoxy-5-methoxybenzaldehyde5-bromo-2-nitrobenzaldehyde o-t-butoxybenzaldehyde2-butoxy-3,S-diiodobenzaldehyde p-s-butylbenzaldehyde4chloro-3-fluorobenzaldehyde 2,3-dichlorobenzaldehyde 2,6-dichloro-3-nitrobenzaldehyde 2,4-diethoxy-S-hexylbenzaldehyde3,5-dimethyl-4-nitrobenzaldehyde pentafluorobenzaldehydepentamethoxybenzaldehyde 2,4,5-trichloro-3,6-dimethoxybenzaldehyde o-,mand p-tolualdehyde 3,5-xylaldehyde (3,5-dimethy1benzaldehyde)2,4,6-triethylbenzaldehyde 2,3,5,6-tetramethylbenzaldehydeisophthalaldehyde 2-methoxy-5-methylisophthalaldehydeS-nitroisophthalaldehyde tetramethylisophthalaldehyde phthalaldehyde4-chlorophthalaldehyde 4,5-dimethoxyphthalaldehyde2,5-dichloroterephthalaldehyde 2,5-diethoxyterephthalaldehyde2,5-dimethylterephthalaldehyde nitroterephthalaldehydetriethylmethylterephthalaldehyde 2-pyridinecarboxaldehyde3-pyridinecarboxaldehyde (nicotinaldehyde) 2,6-pyridinedicarboxaldehyde2- and 3-pyridineacrolein All of the aldehydes described and/or listedherein react with carbon disulfide and an acetylenic compound in thepresence of a phosphine, in the manner taught, to give2-arylidene-1,3-dithioles. All such aldehydes are specifically includedwithin the scope of this invention. Reactions of a wide range ofaldehydes, characteristic of those included in the scope, are set out inthe examples.

Monoaldehydes are preferred. Preferably, the aromatic aldehydes anddialdehydes contain no more than two substituents.

Acetylenic compounds included within the scope of this invention are:

acetylene propiolic acid (propynoic acid) phenylpropiolic acid butylphenylpropiolate phenyl propiolate 3,3,3-trifluoropropyne3,3,4,4,4-pentafluoro-l-butyne 3,4,4, 4-tetrafluoro-3 trifluoromethyl)-1-butyne 1,1,1-trifluoropheny1propyne acetylenedicarboxylic aciddihexyl acetylenedicarboxylate diphenylacetylenedicarboxylateperfluoro-Z-hexyne propiolonitrile perfluoro-3-hexyneacetylenedicarbonitrile (dicyanoacetylene) acetylenedicarbonitrile(butynedinitrile) Preferred are acetylenes in which X is hydrogen,phenyl, lower alkoxycarbonyl, or lower perfluoroalkyl, and Y ishydrogen, phenyl or the same as X.

Phosphines included within the scope of this invention are:

SPECIFIC EMBODIMENTS The following nonlimiting examples are intended toillustrate the invention.

EXAMPLE 1 Dimethyl 2-benzylidene-1,3-dithiole-4,S-dicarboxylate c-ooocmCH P @0110 cs. ii ooooH.

8-0-0 0 OCH:

S- -COOCH:

Tributylphosphine (20.2 g., 0.10 mole) was added dropwise over 10-15minutes to 20 ml. (25.2 g., 0.33 mole) of carbon disulfide with stirringunder nitrogen. Benzaldehyde (15 ml., 15.6 g., 0.15 mole) was added andthe' system was cooled to'5. Dimethyl acetylenedicarboxylate (12.2 g.,0.086 mole) was added dropwise with stirring over about one hour. Themixture was stirred an hour at -5 after addition. Ether (about 50 ml.)was added, and the mixture was filtered to give 10.1 g. (38%) of yellowdimethyl Z-benzylidene-1,3-dithiole-4,5dicarboxylate, M.P. 86-90".Recrystallization from methanol raised the melting point to 94-95".

Analysis.Calcd. for C H O S (percent): C, 54.52; H, 3.92; S, 20.79.Found (percent): C, 54.73; H, 3.91; S, 20.79.

H NMR: Aromatic [5] at 6 7.3, exocyclic CH [1] at 6 6.50, and CH [6] twopeaks at 6 3.83.

UV: In ethanol, A 405 (e 1730), 322 (6 17,700, and 233 nm. (e 14,000).

IR: 1740 (s.), 1725 (s.), 1590 (s.), 1550 (m.), 1490 (m.), 1440 (m.),1250 (s.), 1090 (m.), 1015 (m.), 1000 (m.), 920 (m.), 810 (m.), 770(m.), 760 (m.), 750 (m.), 690 (m.).

EXAMPLE 2 Dimethyl 2- (4-methylbenzylidene) -1,3-dithiole-4,5-dicarboxylate Tributylphosphine (20.2 g.) was addeddropwise to 20 m1. of carbon disulfide under nitrogen. p-Tolualdehyde(15 m1., 15.3 g., 0.13 mole) was added, the mixture was cooled in ice,and a solution of 14.2 g. of dimethyl acetylenedicarboxylate in ml.carbon disulfide was added, dropwise with stirring, over about threehours. Methanol (about 100 ml.) was added, and the mixture was filtered.The filtrate was cooled to 80 and the solid was separated by filtrationto give 9.3 g. (29%) of orange dimethyl 2-(4methylbenzylidene)-1,3-dithiole-4,5-dicarboxylate, M.P. 68-82".Recrystallization from acetone raised the melting point to 85-87".

Analysis.Calcd. for C H O S (percent): C, 55.88; H, 4.38; S, 19.90.Found (percent): C, 55.86; H, 4.44; S, 20.16.

H NMR: C-CH3 [3] at 6 2.32, OCH;, [6] at 6 3.84, exocyclic CH [1] at 66.47, and aromatic CH [4] at 6 7.19.

UV: In ethanol, A 407 (e 1680), 320 (e 18,700), and 233 nm. (a 14,600).

IR: 1740 (s.), 1725 (s.), 1590 (s.), 1510 (m.), 1440 (s.), 1270 (s.),1240 (s.), 1100 (m.), 1020 (m.), 990 (m.), 910 (m.), 850 (m.), 840 (m.),825 (m.), 775 (m.), 760 (m.), 750 (m.), 710 (m.), 680 (m.).

EXAMPLE 3 Methyl 2-benzylidene-1,3-dithiole-4-carboxylate S-CHTributylphosphine (20.2 g.) was added dropwise to ml. of carbondisulfide, followed by 15 ml. of benzalde- S- COOCH3 COOCHa hyde. Themixture was chilled in ice, and dropwise addition of 9 g. (0.11 m.) ofmethyl propiolate was begun with stirring. A solid product began toprecipitate immediately, and its presence made stirring difiicult. Ethylether (ca. 50 ml.) was added, the mixture was allowed to warm to roomtemperature, and dropwise addition of methyl propiolate with stirringwas completed. The mixture was chilled in ice and filtered to give atotal of 9.5 (38%) of crude solid methyl2-benzylidene-1,3-dithiole-4-carboxylate in three crops, the third beingobtained by adding methanol to the previous filtrate and chilling to-70.

After recrystallization from methanol the red product melted at130130.5.

Analysis.Calcd. for C H O S (percent): C, 57.57; H, 4.03; S, 25.62.Found (percent): C, 57.64; H, 4.06; S, 25.63.

H NMR: OCH, [3] at 6 3.83, exocyclic CH [1] two peaks at 6 6.6, andaromatic plus dithiole CH [6] at 6 7.32.

UV: In ethanol, A 385 (e2500), sh. 343 (e 13,500), 324 (6 16,500), and227 nm. (a 14,300). The spectrum in isooctane was virtually unchanged.

IR: 1730 (m.), 1710 (s.), 1580 (s.), 1570 (s.), 1490 (m.), 1440 (m.),1340 (m.), 1290 (s.), 1210 (m.), 1200 (m.), 1160 (m.), 1060 (m.), 1035(m.), 910 (m.), 845 (m.), 830 (m.), 820-(m.),810(m.), 770 (m.), 750(m.), 725 (m.), 690 (m.).

Examples 4-16 were carried out by essentially the procedure illustratedin Examples 1-3. Tenth-molar quantities of phosphine, mono-aldehyde, andacetylenic reactant and excess carbon disulfide were used; 0.05 mole ofeach dialdehyde was used. The product and its properties, together withany significant variation in procedure, are given in each example.

EXAMPLE 4 Dimethyl 2-(4-chlorobenzylidene)-1,3-dithiole-4,5-

dicarboxylate S-C-COOCH: @.CH=C

Tributylphosphine, carbon disulfide, p-chlorobenzaldehyde, and methylacetylenedicarboxylate gave 24.0 g. (70%) of crude product, M.P. 72-79.Recrystallization from methanol gave yellow product which melted atAn-alysis.Calcd. for C -H ClO S percent): C, 49.05; H, 3.23; S, 18.71;Cl, 10.31. Found (percent): C, 49.22; H, 3.32; S, 18.54; Cl, 9.95.

H NMR: OCH [6] at 6 3.89, exocyclic CH [1] at 6 6.47, and aromatic CH[4] centered at 6 7.28.

UV: In ethanol, A 400 (e 1830), sh. 345 (e 17,100), 330 (e 20,600), and233 nm. (e 15,400).

IR: Carbonyl at 1750 cm C=C at 1600 and 1560 cm.- and p-substitutedaromatic absorption at 850 cmr EXAMPLE 5 Methyl2-(4-chlorobenzylidene)-1,3-dithiole-4- carboxylate Tributylphosphine,carbon disulfide, p-chlorobenzaldehyde, and methyl propiolate gave 26.4g. (93%) of yellow dithiafulvene, M.P. 158159. Recrystallization frommethanol-acetone did not raise the melting point.

Analysis.-Calcd. for C H ClO S (percent): C, 50.61; H, 3.18; S, 22.52;Cl, 12.45. Found (percent): C, 50.50; H, 3.26; S, 22.74; Cl, 12.51.

H NMR: In hexadeuteriodimethyl sulfoxide, OCH [3] at 6 3.37, exocyclicCH [1] two peaks at 6 6.2, dithiole CH [1] two peaks at 6 6.8, andaromatic CH [4] at 6 7.4.

UV: In ethanol, A sh. 395 (e 3360), 348 (6 21,400), 337 (e 20,700), and232 nm. (e 16,800).

IR: Carbonyl at 1720 GEL-1, C=C at 1580 and 1560 cmf EXAMPLE 6 Methyl2-(2-nitrobenzylidene)-l,3-dithiole-4- carboxylate SCHTributylphosphine, carbon disulfide, o-nitrobenzaldehyde, and methylpropiolate in 50 ml. of ethyl ether solvent gave 29.9 g. of red product,M.P. 88-89, which precipitated while the methyl propiolate was being 7added. Recrystallization from ethyl acetate raised the melting point to9699.

Analysis.-Calcd. for C H NO S (percent): C, 48.80; H, 3.08; N, 4.75; S,21.70. Found (percent): C, 48.82; H, 3.26; N, 4.77; S, 21.31.

H NMR: OCH;, [3] at 6 3.80, exocyclic CH [1] at 6 6.98, and aromatic anddithiole CH [5] at 6 7.6 to 8.2.

UV: In ethanol, 385 s 6340), 335 (e 9050), and 278 nm. (e 5840). Thespectrum was essentially the same in isooctane.

IR: 3080 (w.), 2980 (w.), 1730 (s.), 1610 (m.), 1575 (s.), 1510 (s.),1470 (m.), 1440 (s.), 1340 (s.), 1285 (s.), 1270 (s.), 1250 (s.), 1210(m.), 1190 (s.), 1145 (m.), 1060 (s.), 945 (m.), 910 (m.), 865 (m.), 860(m.), 850 (m.), 815 (m.), 800 (m.), 785 (m.), 780 (m.), 770 (s.), 730(s.), 700 (m.), 670 (m.).

EXAMPLE 7 Dimethyl 2-(2-nitrobenzylidene)-1,3-dithiole-4,5-

dicarboxylate S-C-COOCHa CH=O S- -COOCH3 Substitution of dimethylacetylenedicarboxylate for methyl propiolate in Example 6 gave 26.5 g.(78%) of yellow product, M.P. 115, which precipitated during addition ofthe diester. Recrystallization from tetrahydrofuran raised the meltingpoint slightly, to 115-116.

Analysis.-Calcd. for C H NO S (percent): C, 47.59; H, 3.14; N, 3.79; S,18.15. Found (percent): C, 47.53; H, 3.12; N, 3.92; S, 18.29.

H NMR: OCH [6] at 6 3.83 and 3.89, exocyclic CH [1] at 6 6.99, andaromatic CH multiplet [4] at 6 7.3 to 8.15.

UV: In ethanol, A 395 (e 6060) and 320 nm. (e 8050). IR: 1740 (s.), 1720(s.), 1600 (s.), 1530 (s.), 1460 (m.),

IR: 1740 (s.), 1720 (s.), 1600 (s.), 1200 (s.), 1100 m.), 1020 (m.), 980(m.), 910 (m.), 860 (m.), 815 (m.), 770 (m), 760 (m.), 740 (m.), 685(m.).

EXAMPLE 8 Tetramethyl 2,2'- (p-phenylenedimethylidyne) bis( 1,3-dithiole-4,S-dicarboxylate) SC-COOCH;

OH=C

s- COOCH:

s-c-cooorr,

s- COOCH;

Tributylphosphine, carbon disulfide, terephthalaldehyde, and dimethylacetylenedicarboxylate gave 16.0 g. (60%) of red dithiafulvene. Afterrecrystallization from ethyl acetate the product melted at 220-225Analysis.Calcd. for C H O S (percent): C, 49.05; H, 3.37; S, 23.82.Found (percent): C, 49.23; H, 3.52; S, 23.47.

H NMR: OCH [6] at 6 3.90, exocyclic CH [1] at 6 6.5, and aromatic CH [2]at 6 7.3.

UV: In ethanol, A 400 (e 40,000) and 384 nm. (6 44,000).

IR: 1760 (s.), 1730 (s.), 1590 (s.), 1510 (m.), 1430 (s.), 1410 (m.),1240 (s.), 1140 (m.), 1090 (s.), 1010 (m.), 995 (m.), 920 (m.), 835(m.), 790 (m.), 770 (m.), 750 (m.), 710 (m.).

8 EXAMPLE 9 Dimethyl 2,2'- (p-phenylenedimethylidyne)bis 1,3-dithiole-4-carboxylate) S-CH CH=C 11 S CO 0 CHI S-CH Substitution ofmethyl propiolate for dimethyl acetylene dicarboxylate in Example 8 gave9.1 g. (43%) of product. After recrystallization from ethylene chloridethe yellow product melted at 257-260.

Analysis.Calcd. for C H O S (percent): C, 51.17; H, 3.34; S, 30.35.Found (percent): C, 51.07; H, 3.41; S, 29.60.

IR: 1710 (s.), 1570 (s.), 1540 (m.), 1430 (m.), 1410 (m.), 1250 (s.),1210 (m.), 1190 (m.), 1050 (m.), 940 (m.), 830 (m.), 770 (m.), 730 (m.).

UV: In methylene chloride, 7\ sh. 403 (6 43,000) and 389 nm. (6 44,700).

EXAMPLE 10 Methyl 2-(3-phenyl-2-propenylidene)-1,3-dithiole-4-carboxylate S-CH S-C-COOCH;

Tributylphosphine, carbon disulfide, cinnamaldehyde, and methylpropiolate in ml. ethyl ether diluent gave 23.9 g. (86%) of crystallineyellow dithiole, M.P. 184- which precipitated during the addition of themethyl propiolate.

Analysis.-Calcd. for C H O S (percent): C, 60.84; H, 4.38; S, 23.21.Found (percent): C, 60.77; H, 4.45; S, 23.56.

H NMR: OCH [3] at 6 3.82, vinyl CH [3] 6 6.1 to 6.5, and aromatic anddithiole CH [6] at 6 7.3.

UV: In ethanol, 3.77 (6 32,100), 3.63 (5 32,900), and 250 nm. (e14,300).

IR: 1710 (s.), 1575 (s.), 1440 (m.), 1290 (s.), 1200 (m.), 1060 (m.),960 (m.), 750 (m.), 730 (m.).

EXAMPLE 11 Methyl 2-(p-nitrobenzylidene)-1,3-dithi0le- 4-carboxylateS-CH Tributylphosphine, carbon disulfide, p-nitrobenzaldehyde, andmethyl propiolate in 100 ml. of ethyl ether diluent gave 19.0 g. of red,crystalline product, M.P. 216 217, which precipitated during theaddition of the methyl propiolate (dissolved in 10 ml. of ethyl ether).Recrystallization from acetone-tetrahydrofuran raised the melting pointto 230-231.

Analysis.Calcd. for C H NO S (percent): C, 48.8; H, 3.08; N, 4.74; S,21.7. Found (percent): C, 48.8; H, 2.95; N, 4.75; S, 21.3.

The H NMR spectrum of the product showed the methoxyl slnglet [3] at 63.84, the exocyclic methine hydrogen [1] at 6 6.57, the dithiole ringhydrogen [1] at 6 7.47, and the aromatic A B pattern [4] at 6 7.3-8.3.

9 EXAMPLE 12 Dimethyl 2- (4-pyridylmethylidyne) -1,3-dithiole-4,5-

dicarboxylate S-C-C O OCH:

S- COOCH:

Tributylphosphine, carbon disulfide, 4-pyridinecarboxaldehyde, anddimethyl acetylenedicarboxylate in 150 ml. of ethyl ether at roomtemperature gave 14.1 g. (46%) of orange dimethyl2-(4-pyridy1methylidyne)-l,3-dithiole-4, S-dicarboxylate, M.P. 140-141".Recrystallization from ethanol raised the melting point to 142.

Analysis.-Calcd. for C H NO S (percent): C, 50.47; H, 3.59; N, 4.53; S,20.73. Found (percent): C, 50.94; H, 3.59; N, 4.59; S, 20.17.

H NMR: Methoxyl [6] at 6 3.80, vinyl hydrogen [1] at 6 6.31 andsymmetrical 4-pyridyl pattern [4] in two areas 6 7 and 8.5.

EXAMPLE 13 Methyl 2- (4-pyridylmethylidyne l, 3-dithiole-4- carboxylateSubstituting methyl propiolate for dimethyl acetylenedicarboxylate inessentially the procedure of Example 12 gave 13.8 g. (55%) of yellowmethyl 2-(4-pyridylmethylidyne)-1,3-dithiole-4-carboxylate, M.P.167-l68. Recrystallization from ethanol raised the melting point to 168-169.

Analysz's.-Calcd. for C H NO S (percent): C, 52.56; H, 3.61; N, 5.57; S,25.52. Found (percent): C, 53.00; H, 3.61; N, 5.81; S, 25.39.

H NMR: OCH [3] at 6 3.82, vinyl CH [1] at 6 6.45, and pyridyl anddithiole CH [5] at low field.

EXAMPLE 14 2-(p-nitrobenzylidene)-1,3-dithiole-4-carboxylic acid S-CHTributylphosphine, carbon disulfide (in 100 ml. of tetrahydrofuran),p-nitrobenzaldehyde, and propiolic acid (in ml. of tetrahydrofuran) gave6.1 g. of crude red 2-(pnitrobenzylidene) 1,3 dithiole 4-carboxylicacid. After recrystallization from tetrahydrofuran, the product meltedat 201-202".

Analysis.-Calcd. for C11H7N04S2 (percent): C, 47.0; H, 2.51; N, 4.98; S,228. Found (percent): C, 46.8; H, 2.47; N, 4.94; S, 22.9.

EXAMPLE l5 Ethyl 2-benzylidene-1,3-dithiole-5-phenyl4-carboxylateS-C-CBHfi S- -COOCH:C a

Tributylphosphine, carbon disulfide (in 100 ml. of ethyl ether),benzaldehyde, and ethyl phenylpropiolate (in 10 ml. of ethyl ether) gave20.4 g. of yellow, crystalline ethyl 2 benzylidene1,S-dithiole-5-phenyl-4-carboxylate, M.P. 110114. Recrystallizaton fromethanol raised the melting point to ll9-120.

Analysis.--Calcd. for C H O S (percent): C, 67.0; H, 4.74; S, 18.8.Found (percent): C, 67.1; H, 4.76.

H NMR: Methyl triplet [3] centered at 6 1.08, methylene (CH quartet [2]centered at 6 4.09, exocyclic methine (CH) singlet [1] at 6 6.43, andaromatic multiplet IR: Carbonyl at 1730 cm.- and double bond absorptionat 1580 and 1540 cmr 10 EXAMPLE 16 Tetramethyl2,2-(tetrachloro-p-phenylenedimethylidyne) bis(l,3-dithiole-4,S-dicarboxylate) Tributylphosphine, carbon disulfide,tetrachloroterephthaldehyde (in ml. of tetrahydrofuran), and dimethylacetylenedicarboxylate (in 10 ml. of tetrahydrofuran) gave 10.7 g. ofyellow tetramethyl 2,2'-(tetrachloro-p-phenylenedimethylidyne)bis(1,3dithiole 4,5-dicarboxylate). After recrystallization fromtetrahydrofuran the product melted at 245-246.

Analysis.Calcd. for C H Cl O S (percent): C, 39.1; H, 2.09; S, 19.0; CI,21.0. Found (percent): C, 39.2; H, 2.39; S, 18.9; C1. 20.8.

H NMR: Methyls as two peaks [6] at 6 3.80 and 3.86 and the exocyclicmethine (CH) singlet [1] at 5 6.3.

IR: Carbonyl at 1720 cm. and double bond absorption at 1590 and 1560cm.-

EXAMPLE 17 2- p-chlo robenzylidene) -4,5-diphenyl-1,3-dithiole S C-C5H5Tributylphosphine (20.2 g.) was added dropwise to 20 ml. of carbondisulfide with stirring under nitrogen. p- Chlorobenzaldehyde (20 g. in70 ml. of ethyl ether) was added, the mixture was chilled in ice, and asolution of 18 g. of diphenylacetylene in 45 ml. of ethyl ether wasadded dropwise with stirring. There was no evidence of reaction. Themixture was warmed to room temperature and stirred overnight, andvolatiles were removed under water-aspirator pressure.1,2-dimethoxyethane (100 ml.) was added, and the mixture was refluxedfor about 18 hours under nitrogen. Volatiles were removed as before. Thecrystals that formed in the residue on standing at room temperature for12 days were separated by filtration, and additional solid product wasobtained by adding methanol (about 30 ml.) to the filtrate. The totalyield of crude 2-(p-chlorobenzylidene 4,5 diphenyl-1,3-dithiole was 23.8g. (63% Recrystallization from ethanol-ethyl acetate gave yellowmaterial melting at 147-148".

Analysis.-Calcd. for C H ClS (percent): C, 69.73; H, 3.99; S, 16.92.Found (percent): C, 69.72; H, 4.09; S, 16.98; Cl, 9.66.

H NMR: Aromatic CH at 6 7.25 and exocyclic CH at 6 6.45.

UV: In ethanol, 360 (6 24,600), 350 (6 25,000) and 243 nm. (e 23,200).

IR: 1600 (m.), 1580 (s.), 1540 (s.), 1490 (s.), 1450 (m.), 1400 (m.),1330 (m.), 1210 (m.), 1100 (m.),1080 (m.), 1010 (m.), 835 (s.), 810(m.), 775 (m.), 770 (m.), 745 (s.), 700 (s.).

EXAMPLE 18 4,5-diphenyl-2-(4-pyridylmethylidyne)-1,3-dithioleTributylphosphine (20.2 g.) was added dropwise to a solution of 25.2 g.of carbon disulfide in 100 ml. of tetrahydrofuran under nitrogen at roomtemperature. 4-pyridinecarboxaldehyde (11 g.) and diphenylacetylene (18g.) were added to the mixture and it was heated at reflux under nitrogenfor 18 hours. The mixture was cooled and low-boiling material wasremoved under water-aspirator pressure. Methanol (30 ml.) was added tothe residue and it was filtered to give 7.2 g. of solid, M.P. 63-100.Recrystallization from ethanol gave yellow 4 ,5- diphenyl 2 (4pyridylmethylidyne)-l,3-dithiole WhlCh melted at 105-106.

Analysis.-Calcd. for C H NS (percent): C, 73.0; H, 4.38; N, 4.06; S,18.6. Found (percent): C, 69.8; H, 4.67; N, 3.78; S, 16.9.

The infrared spectrum showed carbon-carbon double bond absorption at1580, 1530, and 1510 cmr EXAMPLE 194-phenyl-2-(3-phenyl-2-propenylidene)-1,3-dithiole s CH CeHs-CH=CHCH=O AS -COHb By essentially the method of Example 18, except thatcinnamaldehyde (15 g.) and phenylacetylene (12 g.) were substituted for4-pyridinecarboxaldehyde and diphenylacetylene and the mixture washeated at reflux (65) for three days,4-phenyl-2-(3-phenyl-2-propenylidene)-1,3-dithiole was prepared as 3.3g. of solid which melted at 202-203. Recrystallization from ethylacetate gave golden crystals, M.P. 215216.

Analysis.Calcd. for C H S (percent): C, 73.4; H, 4.79; S, 21.8. Found(percent): C, 73.3; H, 4.74; S, 22.0.

UV: In methylene chloride, 7\ 392 (6 33,500) and 260 nm. (6 22,200).

IR: 3100 (m.), 3050 (m.), 1615 (m.), 1600 (m.), 1580 (m.), 1570 (m.),1530 (m.), 1490 (m.),1450(m.), 1335 (m.), 1325 (m.), 1300 (m.), 1285(m.), 1210 (m.), 1180 (m.), 1150 (m.), 1100 (m.), 1070 (m.), 1030 (m.),950 (s.), 920 (m.), 900 (m.), 850 (m.), 840 (m.), 830 (m.), 805 (m.),780 (m.), 740 (s.), 685 (s.).

EXAMPLE 20 2-p-chlorobenzy1idene-4,S-bis(trifluoromethyl)-1,3-

dithiole Tributylphosphine (20.2 g.) was added dropwise to 20 ml. carbondisulfide under nitrogen with stirring, here and throughout the process.The mixture was cooled in an ice bath, and p-chlorobenzaldehyde (20 g.)in 100 ml. of ether was added. Hexafluoro-Z-butyne (17 g.) was passedinto the reaction mixture over a one hour period. The mixture was keptin an ice bath for another two hours. Volatiles were removed in a rotaryevaporator under water-aspirator pressure, and methanol (about 30 ml.)was added to the residue. The solid that precipitated was separated byfiltration, and additional solid was obtained by concentrating andcooling the filtrate. Total yield of yellow2-p-chlorobenzylidene-4,5-bis(trifluoromethyl)-1,3-dithiole was 25.4 g.After recrystallization from methanol the product melted at 7374.

Analysis.-Calcd. for C H ClFe S (percent): C, 39.72; H, 1.39; S, 17.68;C], 9.78; F, 31.42. Found (percent): C, 39.72; H, 1.51; S, 18.08; Cl,9.58; -F, 31.67.

H NMR: Exocyclic CH [1] at 6 6.49 and aromatic CH pattern [4] centeredat 6 7.26.

UV: In ethanol, A 317 (6 16,700) and 224 nm. (e 12,300).

IR: 1620 (m.), 1580 (m.), 1560 (m.), 1490 (m.), 1400 (m.), 1280 (s.),1160 (s.), 1090 (m.), 1010 (m.), 935 (m.), 840 (s.), 810 (m.), 725 (m.),700 (m.).

EXAMPLE 21 2-benzylidene-4,5-bis (trifluoromethyl) -1,3-dithiole s-c-cF;

In essentially the procedure of Example 20, tenth-molar quantities oftributylphosphine, benzaldehyde, and hexafiuoro-Z-butyne and excesscarbon disulfide gave 17.8 g. (54%) of yellow2-benzylidene-4,5-bis(trifluoromethyl)- 1,3-dithiole, M.P. 52-53.Recrystallization from methanol raised the melting point to 57-58".

Analysis.--Calcd. for C H F S (percent): C, 43.90; H, 1.84; S, 19.53; F,34.73. Found (percent): C, 43.92; H, 1.83; S, 20.10; F, 35.32.

H NMR: Exocyclic CH [1] at 6 6.54 and aromatic CH multiplet [5] at 67.3.

UV: In ethanol, x sh. 320 (6 14,400), 310 (5 15,900), sh. 232 (e11,500), and 223 nm. (5 12,500).

IR: 1610 (s.), 1570 (m.), 1490 (m.), 1270 (s.), 1160 (s.), 1150 (s.),930 (m.), 845 (m.), 830 (m.), 810 (m.), 750 (s.), 725 (s.), 700 (m.),685 (s.).

EXAMPLE 22 2-p-nitrob enzylidene-4, 5 -bis trifluoromethyl -1, 3-

dithiole Again in essentially the procedure of Example 20, 0.05- molaramounts of tributylphosphine, p-nitrobenzaldehyde, andhexafluoro-Z-butyne and excess carbon disulfide gave 14.8 g. (79%) ofyellow 2-p-nitrobenzylidene-4,5-bis(trifluoromethyl)-l,3-dithiole, M.P.155-156". Recrystallization from ethanol did not change the meltingpoint.

Analysis.Calcd. for C H F NO S (percent): C, 38.60; H, 1.35; N, 3.76; S,17.18; F, 30.53. Found (percent): C, 38.57; H, 1.35; N, 3.77; S, 17.36;F, 31.21.

H NMR: Exocyclic CH [1] at 6 6.85 and aromatic OH AB pattern [4] at 66.85 to 7.82.

UV: In ethanol, 1 382 (6 18,900) and 251 nm. (e 10,400).

EXAMPLE 23 2-benzylidene-4-phenyl-1,3-dithiole S-C H CaHs-CH=C S C gHsTributylphosphine (20.2 g.) was added over one-half hour to 20 ml. ofcarbon disulfide under nitrogen with stirring. A solution of 20 g. ofbenzaldehyde in m1. of ether was added. A solution of 11 g. ofphenylacetylene in 15 ml. ether was added dropwise with stirring in ice.The mixture was stirred two hours in ice and kept at room temperatureovernight. It was chilled and filtered to give yellow crystals of2-benzylidene-4-phenyl-1,3-dithiole. Several additional crops wereobtained by concentrating and chilling the filtrate. The total yield was12.2 g. (46%). After recrystallization from ethanol the product meltedat 205-206 (lit. M.P. 205-207").

EXAMPLE 24 4-p-nitrobenzylidene-1,3-dithiole S-CH A mixture of 20.2 g.of tributylphosphine, 20 ml. of carbon disulfide, 16 g. ofp-nitrobenzaldehyde, 75 ml. of tetrahydrofuran, and 5 g. of acetylenewas heated at 100 for 8 hours in a closed stainless-steel bomb andcooled. The red crystals of 4-p-nitrobenzylidene-1,3-dithiole in themixture were separated by filtrationand washed with ether. Concentrationand cooling of the filtrate gave two more crops. The total yield was11.2 g. (47%). An analytical sample, M.P. 189-190", was obtained bysublimation at and 0.2 torr.

13 Analysis.-Calcd. for C H NO S (percent): C, 50.61; H, 2.97; N, 5.90;S, 27.02. Found (percent): C, 50.34; H, 2.68; N, 6.06; S, 26.89.

IR: 1590 (m.), 1560 (m.), 1520 (m.), 1500 (m.), 1485 (s.), 1410 (m.),1330 (s.), 1270 (m.), 1245 (m.), 1210 (m.), 1190 (m.), 1110 (s.), 1080(m.), 860 (m.), 850 (m.), 800 (m.), 745 (m.), 690 (m.), 665 (m.).

UV: In methylene chloride, A 392 (6 33,500) and 260 nm. (e 22,200).

EXAMPLE 25 2-p-methylbenzylidene-4-phenyl-1,3-dithiole S C HTributylphosphine (20.2 g.) was added dropwise to 20 ml. carbondisulfide under nitrogen, with stirring here and through the heatingperiod. A solution of 15 g. of p-tolualdehyde in 100 ml. ethyl acetatewas added. A solution of 11 g. of phenylacetylene in 10 ml. of carbondisulfide was then added dropwise, and the mixture was heated at refluxunder nitrogen for 18 hours. Cooling and filtration, followed byconcentration and cooling of the filtrate, gave 5.7 g. (20%) ofZ-p-methylbenzylidene- 4-phenyl-1,3-dithiole in three crops. Afterrecrystallization from ethyl acetate the product melted at 201. Analysiswas carried out on a separate, similarly prepared sample of the yellowproduct.

Analysis.-Calcd. for C H S (percent): C, 72.27; H, 5.01; S, 22.71. Found(percent): C, 72.13; H, 5.27; S, 22.90.

IR: 3080 (w.), 2940 (w.), 1580 (m.), 1560 (m.), 1540 (m.), 1510 (m.),1490 (m.), 1450 (m.), 1410 (m.), 1375 (w.), 1330 (m.), 1210 (w.), 1180(m.), 1130 (m.), 1070 (m.), 1030 (m.), 920 (m.), 900 (m.), 840 (m.), 820(m.), 740 (s.), 705 (m.), 680 (m.).

UV: In ethanol, x 351 (6 22,500) sh. 340 (6 21,900) and 244 nm. (e24,100).

EXAMPLE 26 2-p-chlorobenzylidene-4-phenyl-1,3-dithiole In essentiallythe procedure of Example 25, tenth-molar quantities oftributylphosphine, p-chlorobenzaldehyde, and phenylacetylene and excesscarbon disulfide gave 9.7 g. (32%) of2-p-chlorobenzylidene-4-phenyl-1,3-dithiole. After recrystallizationfrom 1,2-dimethoxyethane the yellow product melted at 237-238".

Analysis.Ca1cd. for C H ClS (percent): C, 63.45; H, 3.66; S, 21.18; Cl,11.70. Found (percent): C, 63.70; H, 3.74; S, 21.10; Cl, 11.67.

UV: In ethanol, A 362 (6 24,600) and 247 nm. (6 23,800).

IR: 1590 (s.), 1580 (m.), 1540 (s.), 1490 (m.), 1450 (m.), 1400 (m.),1340 (m.), 1210 (m.), 1190 (m.), 1120 (m.), 1105 (m.), 1090 (m.), 1075(m.), 1010 (m.), 925 (m.), 840 (s.), 815 (m.), 735 (s.), 700 (m.), 685(m.), 670 (m.).

UTILITY The novel products of this invention are useful for inhibitingvinyl polymerization as shown by the following example.

A solution containing ml. of distilled acrylonitrile, 20 ml. of benzene,0.1 g. of azo-bis(isobutyronitrile), and 3.0 g. of dimethyl2-benzylidene-l,3-dithiole-4,5-dicarboxylate was heated at reflux undera nitrogen atmosphere for three hours. The red solution remainedcompletely clear indicating the absence of polymerization of theacrylonitrile. A control reaction identical except for 14 the absence ofthe benzylidene-dithiole showed initial separation of polymer after 20minutes of heating. After 45 minutes of heating, polymer had completelyfilled the system and prevented stirring.

The products of this invention are also useful as dyes for fabrics. Theyare red, orange and yellow crystalline solids which can be isolated foruse by precipitation with a nonsolvent or by evaporation. Fabrics can bedyed by immersion in a solution of a 2-arylidene-l,3-dithiole indimethylformamide by a conventional vat-dyeing procedure.

I claim:

1. A compound of the formula wherein:

AI is a monovalent or divalent benzene radical unsubstituted orsubstituted with halogen, lower alkyl, lower alkoxy, or nitro, or amonovalent or divalent pyridine radical;

X and Y are hydrogen, lower alkoxycarbonyl, phenyl,

carboxyl, cyano, or lower perfluoroalkyl; and

n is 0 or 1; n is 0 or 1; (mi-n is l or 2; and m is Oor 1;

with the provisos that: when Y==H, (n+n )=1, and m=O, then X phenyl; andwhen X=H, (n+n =1, and m=O, then Y%phenyl.

2. A compound according to claim 1, dimethyl2-benzylidene-l,3-dithiole-4,S-dicarboxylate.

3. A compound according to claim 1, tetramethyl 2,2-(p-phenylenedimethylidyne)bis(1,3 dithiole 4,5-dicarboxylate).

4. A compound according to claim 1, methyl 2-(3- phenyl 2propenylidene)-1,3-dithiole 4 carboxylate.

5. A compound according to claim 1, 4,5-diphenyl-2-(4-pyridylmethylidyne)-1,3-dithiole.

6. A compound according to claim 1, 2-p-chlorobenzylidene-4,5-bis(trifluoromethyl)-1,3-dithiole.

7. A process for making compounds of the formula Ar is a monovalent ordivalent benzene radical unsubstituted or substituted with halogen,lower alkyl, lower alkoxy, or nitro, or a monovalent or divalentpyridine radical;

X and Y are hydrogen, lower alkoxycarbonyl, phenyl,

carboxyl, cyano, or lower perfluoroalkyl; and

n is 0 or 1; n is 0 or 1; (n+n is 1 or 2; andm is Oor 1;

which comprises contacting and reacting an aromatic aldehyde with carbondisulfide and an acetylenic compound in the presence of atrihydrocarbylphosphine of the formula R P wherein the Rs may be thesame or dilferent and are lower alkyl, cycloalkyl of 5 or 6 carbons, orphenyl (lower alkyl), and at a temperature between about -50 C. and 200C.

8. A process according to claim 7, comprising sequentially:

(a) mixing the carbon disulfide and phosphine to form a loose complex,and

(b) contacting this complex with the aromatic aldehyde and theacetylenic compound.

9. A process according to claim 7 wherein all R groups are the same andare lower alkyl.

10. A process according to claim 7 wherein the aromatic aldehyde isbenzaldehyde and the acetylenic compound is dimethylacetylenedicarboxylate.

11. A process according to claim 7 wherein the aromatic aldehyde isterephthalaldehyde and the acetylenic compound is dimethylacetylenedicarboxylate.

16 12. A process according to claim 7 wherein the aro- Reference Citedmatic aldehyde is cinnamaldehyde and the acetylenic com- Mayer et a1 LPram Chem 4th Series, VOL 35, pound iS methyl propiolate. 294 to 0 19 713. A process aCCOldHlg to clalm 7 wherein the aro- Kirmse et a1. 614(1958).

matic aldehyde is pyridinecarboxaldehyde and the acety- 5 Behringer eta1 Tetrahedron utters, v01. 20, pp. 1895 lenic compound isdiphenylacetylene. 1899 (1967).

14. A process according to claim 7 wherein the aromatic aldehyde isp-chlorobenzaldehyde and the acetylenic JOHN D RANDOLPH Primary Examinercompound is hexafluoro-Z-butyne.

15. A process according to claim 7 wherein the aromatic aldehyde isbenzaldehyde and the acetylenic com- 10 pound is phenylacetylene.252-380; 26088.7 D, 240 R, 240.1, 327 M

